Here are some CSS resource links:
http://www.csszengarden.com/ This is my favorite CSS site because it shows how the same text can be represented entirely differently. This site reminds me that only 8% of the meaning of communication comes from the text of the words. 92% comes from intonation and nonverbals.
http://www.w3schools.com/css/ Looks good
http://www.mezzoblue.com/css/cribsheet/ is a long blog post
http://websitetips.com/articles/css/ has articles, tutorials and tips, SEO too
http://www.westciv.com/ for sale, has a product
http://www.davesite.com/webstation/css/ an intro, not much of a site